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Lead‐free Cs2AgBiBr6 double perovskite is considered a promising alternative photovoltaic absorber to the widely used lead halide perovskite due to its easy processability, high stability, and reduced toxicity. Herein, for the first time spray processing for the deposition of Cs2AgBiBr6 double perovskite thin films is reported. Microstructural (X‐ray diffraction, scanning electron microscopy) and optoelectronic (absorbance, photoluminescence, photocurrent density versus applied voltage curves, electrochemical impedance spectroscopy) properties of spray‐coated film are compared with the spin‐coated benchmark. Incorporation of the spray‐coated Cs2AgBiBr6 double perovskite thin films in solar cells leads to a 2.3% photoconversion efficiency with high open‐circuit voltage of 1.09 V. This study highlights the suitability of ultrasonic spray deposition for the optimization of Cs2AgBiBr6 solar cells in terms of light absorption properties and charge transfer at the Cs2AgBiBr6/hole transporting layer interface.

Perovskite solar cells have shown a tremendous interest for photovoltaics since the past decade. However, little is known on the influence of light management using photonic crystals inside such structures. We present here numerical simulations showing the effect of photonic crystal structuring on the integrated quantum efficiency of perovskite solar cells. The photo-active layer is made of an opal-like perovskite structure (monolayer, bilayer or trilayer of perovskite spheres) built in a TiO 2 matrix. Fano resonances are exploited in order to enhance the absorption, especially near the bandgap of perovskite material. The excitation of quasi-guided modes inside the absorbing spheres enhances the integrated quantum efficiency and the photonic enhancement factor. More specifically, a photonic enhancement factor as high as 6.4% is predicted in the case of spheres monolayer compared to an unstructured perovskite layer. The influences of sphere's radius and incident angle on the absorbing properties are also estimated. Those numerical results can be applied to the nascent field of photonic structuring inside perovskite solar cells.

A c c e p t e d M a n u s c r i p tThe intercalation and de-intercalation of lithium cations in electrochromic tungsten oxide thin films are significantly influenced by their structural and surface characteristics.In this study, we prepared two types of amorphous films via the sol-gel technique: one dense and one mesoporous in order to compare their response upon lithium intercalation and deintercalation.According to chronoamperometric measurements, Li + intercalates/de-intercalates faster in the mesoporous film (24s/6s) than in the dense film (48s/10s bronze.

In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting). Because the activation of the dopant requires a heat treatment at high temperature (≥ 800°C), it usually results in the collapse of the mesostructure. We have overcome this obstacle by using a temporary SiO 2 scaffold to hinder crystallite growth and thereby maintain the mesoporosity. The beneficial effect of the activated dopant has been confirmed by comparing the photocurrent of doped and undoped films treated at different temperatures. The role of the mesostructure was investigated by comparing dense, collapsed and mesoporous films heated at different temperatures and characterized under front and back illumination. It turns out that the preservation of the mesotructure enables a better penetration of the electrolyte into the film and therefore, reduces the distance that the photogenerated holes have to travel to reach the electrolyte. As a result, we found that mesoporous films with dopant activation at 850°C perform better than comparable dense and collapsed films.